The invention relates in particular to a motor vehicle transmission device with an activating unit.
European Patent Document EP 0 512 727 B1 discloses a motor vehicle transmission device of generic type, having an actuating unit, which is formed by a central control unit and which is intended to cancel a tooth-on-tooth position of two claw coupling elements. In so doing the actuating unit is intended to engage a disconnect clutch for a brief period before disengaging it again.
The invention provides a motor vehicle transmission device, in which improved characteristics in terms of the dynamic behavior and comfort can be achieved. The invention includes a motor vehicle transmission device having an actuating unit, which is used to cancel a tooth-on-tooth position of coupling elements, and, in particular claw coupling elements.
The actuating unit activates a transmission brake in the event of a tooth-on-tooth position. A transmission brake in this exemplary embodiment, is taken to mean, in particular, a unit which is intended for braking a transmission, especially in order to effect a process of synchronization. An actuating unit is taken to mean, in particular, a closed-loop and/or open-loop control unit, which preferably comprises a computer unit and a memory unit having a corresponding program for the actuation or open-loop and/or closed-loop control of the transmission brake. The term ‘intended’ is furthermore taken to mean, in particular, that the unit is specially equipped, designed and/or programmed to carry out the described functions.
According to examples of the invention, an advantageously short delay time can be achieved between activation of the transmission brake and its action on the coupling elements. In particular, it is possible to achieve a shorter delay time compared to a disconnect clutch arranged between an internal combustion engine and a motor vehicle transmission. A significant reduction in the average time taken for meshing of the coupling elements or the claw coupling elements can be achieved. The transmission brake can be arranged in proximity to the coupling elements, so that an advantageous power transmission or torque transmission can be achieved from the transmission brake to the coupling elements. In particular, it is possible to avoid a torque transmission for the purpose of resolving a tooth-on-tooth position by way of a splitter box. It is moreover possible to improve the comfort, in that a transmission brake, in particular, can be controlled particularly precisely and reproducibly and fundamentally more so than a disconnect clutch between the internal combustion engine and the motor vehicle transmission. A transmission brake furthermore, in this example, has a limited maximum transmissible torque, thereby at least largely avoiding impact shocks inherent in the system.
In a further development of the invention the motor vehicle transmission device comprises the transmission brake formed by a multi-disk brake. Embodying the transmission brake as a multi-disk brake means that the device can be integrated in an especially simple and compact design, especially if an actuator unit acts upon the disks of the multi-disk brake in order to generate a friction force with a normal force. The transmission brake is advantageously intended for braking a countershaft and for this purpose is most preferably coupled directly to the countershaft, so that the transmission brake can advantageously be used for the synchronization.
In an exemplary embodiment, the motor vehicle transmission device comprises a rheological brake unit, and in particular a magneto-rheological brake unit, a braking action can be adjusted with particular speed and precision. A rheological brake unit, according to this example, includes a brake unit having a medium, the consistency of which can be varied in order to obtain a braking effect. For example, the medium may be a magneto-rheological fluid, the consistency of which can be varied by a magnetic field, preferably continuously from a liquid to an at least largely solid consistency. A magneto-rheological fluid is, for example, a suspension of small magnetically polarizable particles, which are finely dispersed in a carrier liquid. These are generally iron particles in an oil. In a magnetic field the particles are polarized and are ordered in chains along field lines of the magnetic field. The formation of structures causes the suspension to become stiffer. Once the magnetic field is switched off the consolidated material reverts to its original fluid state.
In exemplary embodiments, the motor vehicle transmission device includes a transmission brake formed by a motor-driven brake unit, so that a drive torque opposed to a brake torque may advantageously be generated by the motor-driven brake unit, at least under certain operating parameters, in order to cancel a tooth-on-tooth position. The motor-driven brake unit may be formed by different units that would appear suitable to a person skilled in the art, but to particular advantage would be gained by an exemplary embodiment using an electric motor unit.
The actuating unit is furthermore intended to actuate the transmission brake at least as a function of an operating parameter registered during operation, in order to cancel a tooth-on-tooth position, with the advantage that account can purposely be taken of prevailing marginal conditions. The transmission brake can basically be actuated as a function of various operating parameters that would be found suitable by a person skilled in the art, such as a current gear of the transmission or a gear to be selected and/or advantageously as a function of an acting pressure, a torque build-up or torque profile and/or an acting force, such as, in particular, a force acting on the transmission brake itself. For this purpose the actuating unit preferably has a sensor unit for sensing the operating parameter, although sensor units external to the actuating unit may also be used. Signals picked up from corresponding external sensor units could then preferably be relayed to the actuating unit via bus systems.
In exemplary cases where the actuating unit for actuating the transmission brake has a learning function and is intended to learn, via the learning function, at least one operating parameter for actuating the transmission brake, a self-adapting and optimizing system can advantageously be obtained. An advantageous value can preferably be determined, indicating for example how long and/or with what pressure the transmission brake is preferably and/or purposely to be actuated in the event of specific operating parameters.
In a further embodiment of the invention, the actuating unit is intended to repeatedly actuate or activate the transmission brake in at least one pulsating operating mode in order to cancel a tooth-on-tooth position, thereby advantageously reducing the wear, especially by avoiding unnecessarily high stress loads on the transmission brake, particularly when the transmission brake, over time, is correspondingly activated at greater time intervals and/or at an increased pressure in order to obtain a greater braking action.
The motor vehicle transmission device in further embodiments has an actuating unit for actuating a disconnect clutch, the actuating unit being intended, that is to say being specially designed, equipped and/or programmed to actuate the disconnect clutch when a tooth-on-tooth position is detected, in order to generate a pulse on the coupling elements and thus to cancel the tooth-on-tooth position. The disconnect clutch can advantageously be used also to cancel a tooth-on-tooth position when a motor vehicle is stationary. Unacceptably high torques and/or stresses of the transmission brake can furthermore be avoided by using the disconnect clutch for stronger rotational pulses. A disconnect clutch is here taken to mean, in particular, a clutch which is arranged between an internal combustion engine and a motor vehicle transmission, such as a torque converter, for example, a torque converter lockup clutch and/or in particular an automated friction clutch.
The actuating unit for actuating the transmission brake and the actuating unit for actuating the disconnect clutch are preferably intended for actuation in coordination with one another, in order to cancel a tooth-on-tooth position, or the actuating units are preferably functionally coupled so that desired interactions can purposely be obtained, in which the disconnect clutch, for example, can be activated as a function of a number of pulses of the transmission brake. It is also feasible, depending on the action of the transmission brake and/or of the disconnect clutch, for the actuating unit in question to undertake a correspondingly coordinated actuation of the other unit.
The actuating units may be coupled in various ways that are known in the art, for example in respect of a pulse duration, a number of pulses, etc. The actuating unit for actuating the transmission brake and the actuating unit for actuating the disconnect clutch are advantageously intended to activate the transmission brake and the disconnect clutch at least substantially at the same time. According to examples of the invention, the disconnect clutch fundamentally has a longer delay time, so that two successive pulses to the coupling elements can advantageously be obtained, that is firstly a smaller pulse by using the transmission brake and then a larger pulse by using the disconnect clutch. Should it prove impossible to cancel the tooth-on-tooth position by using the smaller pulse initiated by the transmission brake, the tooth-on-tooth position can be cancelled without time delay by using a larger pulse, initiated by the disconnect clutch, as distinct from a general actuation of the disconnect clutch. The term ‘substantially at the same time’ is here taken to mean that an exemplary period of less than 40 msec elapses between the activation times of the disconnect clutch and of the transmission brake.
In a further exemplary embodiment of the invention the actuating unit for actuating the transmission brake and the actuating unit for actuating the disconnect clutch are at least in part integrally formed, thereby saving on additional components, overall dimensions, weight, assembly effort and costs.
Further advantages are set forth in the following description of the drawing.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.